In recent decades, high-order harmonic generation (HHG) from atoms [1]}, [2]}, [3]}, molecules [4]}, [5]}, [6]} and solids [7]}, [8]}, [9]}
has been a hot subject in experimental and theoretical studies of strong laser-matter interaction. The HHG has shown its promising
applications as a seed to generate attosecond pulses. It can also be used as a unique tool to probe the ultrafast dynamics of electrons within atoms and molecules
with unprecedent attosecond resolution.
